Why Can We See the Corona Sphere During a Solar Eclipse?

[Psyguy22]

In basic, why can we only see the corona sphere during a solar eclipse? Is there a property to the eclipse or sun that causes this?

 

[chemisttree]

The blue sky washes out the corona. A dark sky in the daytime is a must so an eclipse it is. Above the atmosphere, a simple disk placed over the image of the sun will work.

 

[Chronos]

There is a device called a coronascope that is useful for this purpose.